Horner syndrome

What it is

Horner syndrome is sympathetic denervation of the face. The ocular sympathetic pathway runs in three neurons. The first, called central, begins in the hypothalamus and runs down to the spinal cord. The second, preganglionic, comes out of the cord at the level named the center of Budge, C8 to T2, runs near the lung and goes up to the superior cervical ganglion. The third, postganglionic, runs along the internal carotid artery and goes to the eye through the nasociliary and the long and short ciliary nerves, to the iris dilator muscle and the superior tarsal muscle, also named Muller's muscle, with sudomotor and vasoconstrictor fibers to the face.

How it presents

Three findings are grouped together under PAM. Ptosis, a slight drooping of the eyelid, from the superior tarsal muscle. Anhidrosis, absence of sweating, with flushing of the affected side of the face. Miosis, constriction of the pupil, so the two pupils are unlike each other, that is anisocoria. Enophthalmos, a sunken eye, is listed with them, although the appearance is due to a narrow palpebral aperture rather than to true enophthalmos. The ptosis is mild.